Glycerol is generally required to have low level of color (APHA) for practical quality. In purification of glycerol from a crude glycerol, efficient reduction of color (APHA) is thus required. Particularly in production of glycerol that meets Japanese Standards of Cosmetic Ingredients, is employed a method including subjecting the crude glycerol to pretreatments such as distillation and filtration to remove oils and inorganic matters as much as possible, and removing a trace amount of impurities from the treated crude glycerol product liquid or reducing a level of color (APHA) of the treated crude glycerol product liquid (JP-A10-218810 and JP-A6-184024).
JP-A10-218810 discloses production of glycerol using a solid catalyst. EP-A1978009 and US-A2009-030243 disclose purification of glycerol with an ion-exchange resin.